Tanana State Soil

Soil Science Society of America

Introduction Many states have a designated state bird, flower, fish, , rock, etc. And, many states also have a state soil – one that has significance or is important to the state. The Tanana is the official state soil of Alaska. Let’s explore how the Tanana is important to Alaska. History The Tanana series is found only in Alaska and was established in the -Tanana Area in 1914. It was named after the Tanana River, whose name in-turn was derived from the Athabaskan word for “Mountain River.” The Tanana soil was chosen by Alaskan soil scientists because it is a soil, a property in the that is unique to Alaska. Tanana soils range widely through the interior of Alaska and when cleared can thaw and become productive farm land. What is Tanana Soil? Under mature native , Tanana soils are poorly drained and contain per- mafrost within 50 inches of the surface. If the surface vegetation and organic mat is disturbed, either through wildfire or cultural activities such as farming, the soil will warm and become well drained. Tanana soils are on flood plains and alluvial terraces (a river terrace of alluvium-material transported and deposited by moving water- rather than carved in solid rock. When undisturbed and frozen, Tanana soils support a native community of black spruce, shrubs and feather moss. When thawed, white spruce and paper dominate. When cleared and developed for agriculture, Tanana soils are used for hay, pasture, small grains, and vegetables. Every soil can be separated into three separate size fractions called sand, silt, and clay, which makes up the soil texture. They are present in all soils in different propor- tions and say a lot about the character of the soil. Undisturbed, Tanana soils have an organic layer that ranges from 2 to 8 inches thick. This organic material is slightly to moderately decomposed and derived mostly from moss. The top soil is black mucky silt loam enriched with highly decomposed or- ganic material called humus. The sub soil is gray and light olive-brown stratified silt loam and very fine sandy loam that has streaks and pockets of black mucky material moved from above. These streaks and pockets are caused from a process called cryo- turbation. , or frost churning, causes a mixing of soil horizons due to freezing and thawing. The subsoil of an undisturbed Tanana is permanently frozen silt loam and very fine sandy loam. This frozen soil limits root growth and also perch- es the water table causing the soil to be poorly drained. When disturbed, Tanana soils thaw, which allow free drainage and the soil becomes well-drained. Once thawed, deeper observation of the soil can be made and a sandy and gravelly substratum can sometimes be found, usually below 3 feet (Figure 1).

Photo Soil Monolith: Chip Clark/Smithsonian Institution Fig. 2. Location of the Tanana soil in Alaska. Credit: Smith- sonian Institution’s Forces of Change.

Fig. 3 Alaskan Cabbage from Fair. Credit: Alaska USDA-NRCS.

Fig. 1. Thawing Tanana soil. Credit:Alaska USDA-NRCS.

Where to dig Tanana Yes, you can dig a soil. It is called a soil pit and it shows you the ditions, wildlife habitat and recreational uses are plenty. When soil profile. The different horizontal layers of the soil are called altered, they support a of aspen, paper birch, and white soil horizons. This does not mean that other types of soil can- spruce which will also provide adequate habitat for wildlife and not be found there but that the Tanana is very common. Tanana recreation. When cultivated, Tanana soils are used for farming. soils exist in the interior of Alaska on the flood plains and low Due to nearly constant sunlight throughout the , some terraces of rivers. They occur in the Fairbanks North Star Bor- crops can grow to an enormous size. Examples include a 19 ough, Borough, the Yukon-Koyukuk Census Area and the pound carrot, a 76 pound rutabaga, and a 106 pound cabbage Southeast Fairbanks Census Area (Figure 2). Tanana soil may (Figure 3). cover an estimated 3 to 5 million acres though a very small por- When Tanana soils are allowed to thaw and drain they have few tion of its range has actually been mapped. Most commonly, it limitations. The process changes the soil so drastically it actually will be found under a stunted black spruce forest, but if the site becomes a different soil. When thawed, Tanana typically changes has been disturbed, the forest may be white spruce and birch or to recognized soils Salchaket or Jarvis. Areas that were histori- being farmed. In all, there are a total of 561 named soils (series) cally Tanana soils now support homes, urban areas, roads and in Alaska. streets, parks, as well as agriculture Importance Limitations What makes the Tanana soil so important is its use and preva- When a soil cannot be used for one or more of the described lence in the State. When undisturbed, Tanana soils support a functions, it is referred to as a limitation. Soil experts, called Soil wetland forest of black spruce and shrubs that support an abun- Scientists, studied Tanana soil and identified that, under natural dance of wildlife and recreation. They are unique in that they conditions it has permafrost limitation. Permafrost in this soil are permanently frozen below 50 inches. Wild fire or human impedes the internal drainage causing the soil to be wet. The disturbance, such as plowing, will cause the soil to warm and dry, cold, hard layer of permafrost also limits the rooting depth for significantly altering its characteristics. After thawing, Tanana . Since this soil occurs on floodplains there is also risk soils support hay, grains, potatoes and cool vegetables. of flooding. The restricted drainage make Tanana soils poorly suited for things such as trails, camp grounds and waste disposal. Uses Wind and water erosion are a concern on areas that have been cleared of native vegetation. In general, soils can be used for agriculture (growing foods, rais- ing animals, stables); engineering (roads, buildings, tunnels); ecology (wildlife habitat, wetlands), recreation (ball fields, play- ground, camp areas) and more. Tanana soils are important for all of these uses in Alaska. Under natural black spruce forest con-

2 Fig. 4. (Above) Extreme conditions under which Tanana soils develop. Credit:Alaska USDA-NRCS Staff, Brant Dallas.Fig. 5. (Above right) Black spruce and moss environment that greatly influence soil pH. Credit:Alaska USDA-NRCS Staff, Blaine Spellman. Fig. 6. (Inset) Young bull grazing on willow shrubs. Credit: Cory Cole

Management In its natural state Tanana is typically managed for wildlife habitat exceed 90 degrees F (32 degrees C) while extreme winter and limited recreation. Tanana soils support a black spruce forest temperatures may dip below -60 degrees F (-51 degrees C). with an ericaceous (heather) shrub and moss understory. Animals The average annual is 12 inches (30 cm), with typically encountered include moose, grouse, snowshoe hares, and July and August being the wettest months and April the driest. many various song birds. The shrub layer provides many variet- Snow covers the ground continuously from October to late ies of wild berries including blue berries (Vaccinium uliginosum), April or early May. These strong freeze thaw cycles cause lingonberries (low bush cranberries)(Vaccinium vitis-idaea) and cryoturbation in the soil. cloud berries(Rubus chamaemorus). Common management strat- Organisms – This refers to plants and animal life. In the egies to protect against wind and water erosion are recommended soil, plant roots spread, animals burrow in, and bacteria break in areas where native vegetation has been cleared. down plant and animal tissue. These and other soil organisms speed up the breakdown of large soil particles into smaller Tanana Formation ones. Plants and animals also influence the formation and differentiation of soil horizons. Plants determine the kinds Before there was soil there were rocks and in between, CLORPT. and amounts of organic matter that are added to a soil under Without CLORPT, there will be no soil. So, what is CLORPT? normal conditions. Animals breakdown complex compounds It is the five major factors that are responsible for forming a soil into small ones and in so doing add organic matter to soil. Ta- like the Tanana series. It stands for , Organisms, Relief, nana soils typically support a black spruce forest with a shrub Parent material and Time. CLORPT is responsible for the de- understory. These plants contribute organic acids to the soil velopment of soil profiles and chemical properties that differenti- causing the Tanana soil to be acid or have a low pH in its ate soils. So, the characteristics of Tanana (and all other soils) upper horizons (Figure 5). Common mammals in the area are determined by the influence of CLORPT. Weathering takes include brown and black bear, moose, wolf, lynx, furbearers place when environmental processes such as rainfall, freezing and rodents (Figure 6). Birds are attracted to the wet, boggy and thawing act on rocks causing them to dissolve or fracture forest for the plethora of insects to eat. Spruce hens and rough and break into pieces. CLORPT then acts on rock pieces, marine grouse also frequent to the area. sediments and vegetative materials to form soils. Relief – Landform position or relief describes the shape of the land (hills and valleys), and the direction it faces which Climate – Temperature and precipitation influence the rate at makes a difference in how much sunlight the soil gets and which parent materials weather and dead plants and animals how much water it keeps. Deeper soils form at the bottom of decompose (Fig. 4). They affect the chemical, physical and the hill rather than at the top because gravity and water move biological relationships in the soil. Tanana soils occur in an soil particles downhill. Tanana soils occur on floodplains and area that has a continental climate with long, cold low terraces so the relief is very flat with slopes usually not and short, warm . Summer (June, July, and exceeding 2% (Figure 7). These very flat surfaces, combined August) temperatures average 58 degrees F (15 degrees C). with the permafrost do not allow the soil to drain, resulting Winter (November through March) temperatures average 0.5 in the poorly drained condition of the Tanana soil (Figure 8). degree F (-18 degrees C). Extreme summer temperatures may

3 Fig. 7. Diagram of a landscape showing relationship of soil series, underlying material, and permafrost. Adapted from Pewe (Soil Survey of Fairbanks Area, Alaska; 1959).

Parent material (C horizon) – Just like people inherit charac- teristics from their parents, every soil inherits some traits from the material from which it forms. Some parent materials are transported and deposited by , wind, water, or gravity. Tanana soils occur on flood plains and low terraces so the par- ent material is primarily alluvium with the addition of loess. Alluvium is material that has been transported and deposited by moving water. Loess is silty material that has been trans- ported and deposited by wind. Time – All the factors act together over a very long period of time to produce soils. As a result, soils vary in age. The length of time that soil material has been exposed to the soil- forming processes makes older soils different from younger soils. Generally, older soils have better defined horizons than younger soils. Less time is needed for a soil profile to develop in a humid and warm area with dense vegetative cover than in a cold dry area with sparse plant cover. More time is required for the formation of a well-defined soil profile in soils with fine textured material than in soils with coarse-textured soil material. The alluvium that forms the Tanana soil is Holocene in age so it is fairly young, by soil standards.

Fig. 8. Aerial view of Tanana Flats Landscape. Photo courtesy of Blaine Spellman.

4 Fig. 9. Alaska Ecoregions, ftp://newftp.epa.gov/EPADataCommons/ORD/Ecoregions/ak/ak_eco.pdf

Ecoregions, Soils and Land Use in Alaska Geology The Interior Bottomlands Ecoregion of Alaska includes the flood Although never glaciated, this area is filled with a deep layer of plains and terraces along the upper reaches of the Tanana and Pleistocene age glaciofluvial deposits. Additional fluvial sedi- Kuskokwim Rivers and the middle reaches of the ments have accumulated along the major rivers and their tribu- (Fig. 9). The area makes up about 36,320 square miles (94,120 taries during the Holocene epoch. Much of the interior of Alaska square kilometers). This ecoregion includes Alaska’s second larg- is mantled with a layer of silty micaceous loess originating from est city, Fairbanks; as well the towns of , Delta Junction, the unvegetated flood plains and outwash plains of the Interior and Tok on the road system. The communities of Tanana, Galena, Bottomlands Ecoregion. and McGrath are accessible only by air or by river. Also within the ecoregion are parts of Fort Wainwright and Fort Greely, the Climate two largest military reservations in Alaska as well as Portions of Denali National Park and Preserve and Tetlin National Wildlife The interior of Alaska has a sub-arctic charac- Refuge. Portions of the Trans-Alaska Pipeline traverses this area terized by Short, warm summers and long, very cold winters. The as it makes its 800 mile journey from the Prudhoe Bay in the average annual precipitation ranges from 10 to 20 inches (255 to north to Valdez in the south. 510 millimeters). Most precipitation occurs in late summer, mainly from thunderstorms. About half the annual precipitation comes as Physiography Snow. The average annual snowfall ranges from 30 to 80 inches (75 to 205 centimeters). The average annual temperature ranges The Interior Bottomlands Ecoregion is on broad, nearly level, from about 22 degrees F to 28 degrees F (-6 to -4 degrees C). Win- braided and meandering flood plains, stream terraces, and outwash ter temperatures are often colder than -70 degrees F and have been plains. These lowlands are dotted with hundreds of lakes and wet- recorded near 100 degrees F in the summer. The freeze free period lands. Elevation ranges from about 100 feet (30 meters) along averages about 70 to 120 days. The temperature usually remains the lower Yukon River, to about 1,900 feet (580 meters) in the up- above freezing from June through mid-September. perTanana Valley. This area is in the zone of discontinuous perma- frost. Permafrost is close to the surface in areas of the finer textured alluvial and eolian sediments on plains and stream terraces, Glossary Additional Resources Alluvium: Sediments deposited by running water of streams and Soil! Get the Inside Scoop. David Lindbo and others. Soil Science Society rivers. It may occur on terraces well above present streams, on the of America, Madison, WI. present flood plains or deltas, or as a fan at the base of a slope. Know Soil, Know Life. David L. Lindbo, Deb A. Kozlowski, and Clay Rob- Clay: A soil particle that is less than 0.002 mm in diameter. Clay inson, editors. Soil Science Society of America, Madison, WI. particles are so fine they have more surface area for reaction. They hold a lot of nutrients and water in the soil. A clay soil is a soil that has more than 40% clay, less than 45% sand and less than 40% silt. Web Resources Cryoturbation: The mixing of soil layers, due to repeated freeze/thaw Soils for Teachers—www.soils4teachers.org processes results in irregular or broken horizons, accumulations of Soils for Kids—http://www.soils4kids.org/ organic matter on the permafrost table, oriented rock fragments, and Have Questions? Ask a Soil Scientist—https://www.soils.org/ask silt caps on rock fragments. Soil Science Society of America—https://www.soils.org/ Eolian: Pertaining to earth material transported and deposited by the wind including dune sands, sand sheets, loess, and parna. Loess: Material transported and deposited by wind and consisting dominantly of silt-sized particles Authors: Dennis Mulligan, Soil Scientist, USDA - Natural Resources Ecoregion: Represents areas with similar biotic and abiotic charac- Conservation Service, Alaska teristics which determine the resource potential and likely responses Cory Cole, State Soil Scientist, USDA - Natural Resources to natural and man-made disturbances. Characteristics such as cli- Conservation Service, Alaska mate, topography, geology, soils, and natural vegetation define an ecoregion. They determine the type of land cover that can exist and influence the range of land use practices that are possible. Glaciofluvial Deposits: Material moved by glaciers and subsequent- ly sorted and deposited by streams flowing from the melting ice. Horizon: see Soil horizons Organic matter: Material derived from the decay of plants and ani- mals. Always contains compounds of carbon and hydrogen. Holocene: The geological period comprising approximately the last 10,000 . Permafrost: A thermal condition in which a material (including soil material) remains below 32° F for 2 or more years in succession. Sand: A soil particle between 0.05 and 2.0 mm in diameter. Sand is also used to describe soil texture according to the soil textural tri- angle, for example, loamy sand. Silt: A soil particle between 0.002 and 0.05 mm diameter. It is also used to describe a soil textural class. Soil Horizon: A layer of soil with properties that differ from the layers above or below it. Soil Profile: The sequence of natural layers, or horizons, in a soil. It extends from the surface downward to unconsolidated material. Most soils have three major horizons, called the surface horizon, the sub- soil, and the substratum. Soil Scientist: A soil scientist studies the upper few meters of the Earth’s crust in terms of its physical and chemical properties; distri- bution, genesis and morphology; and biological components. A soil scientist needs a strong background in the physical and biological sciences and mathematics. Soil Texture: The relative proportion of sand, slit, and clay particles that make up a soil. Sand particles are the largest and clay particles the smallest. Learn more about soil texture at www.soils4teachers. org/physical-properties

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This state soil booklet was developed under the auspices of the Soil Science Society of America’s K-12 Committee—their dedication to developing outreach materials for the K-12 audience makes this material possible.